1. Field of the Invention
The present invention relates to an electronic apparatus, and particularly to an electronic apparatus provided with a function module such as a sensor, and a multilayer circuit board for trunk connecting an output signal wiring of the function module to a coaxial cable.
2. Description of the Prior Art
A configuration shown in FIG. 21 will be explained as one for a sensor device of a prior art example. FIG. 21 is a perspective view showing the sensor device of the prior art example. In a sensor module 2001 used as a function module, one end of a signal wiring 2003 of a multilayer wiring unit thin-film formed on the surface of a substrate is connected to a signal pad 2004, and one end of each ground wiring 2005 of the multilayer wiring unit is connected to a ground pad 2006. When the signal wiring 2003 is now located within an internal layer, the signal wiring 2003 is led to the top layer through a via. In a multilayer wiring board 2002, one end of a signal wiring 2007 is connected to a signal pad 2008, and the other end thereof is connected to a signal pad 2013, whereas one end of each ground wiring 2009 is connected to its corresponding ground pad 2010, and the other end thereof is connected to its corresponding ground pad 2014. Further, the sensor module 2001 is fixedly secured to the multilayer circuit board 2002. The signal pad 2004 and the signal pad 2008 are connected to each other by a bonding wire 2011, and the ground pads 2006 and the ground pads 2010 are connected to one another by bonding wires 2012 respectively. Then, a central conductor 2016 of a semi-rigid coaxial cable 2015 is connected to the signal pad 2013 by using solder or the like, and an outer conductor 2017 of the semi-rigid coaxial cable 2015 is connected to the ground pad 2014 by use of solder or the like.
Incidentally, a configuration of connecting the multilayer circuit board and the semi-rigid coaxial cable has been disclosed in Japanese Published Unexamined Patent Publication Nos. 2001-102817 and 2001-320208 by way of example.
However, in the configuration of the sensor device illustrative of the prior art example, which is shown in FIG. 21, a problem arises in that sine the multilayer wiring unit of the sensor module 2001, and the signal wirings, pads and bonding wires of the multilayer circuit board 2002 are exposed, they are susceptible to an outcoming noise. Also a problem arises in that a high-frequency signal transmission characteristic is apt to be degraded due to the resistance of each bonding wire and the influence of impedance. Further, a problem arises in that the sensor device is sensitive to a mechanical shock associated with soldering even if an attempt is made to directly solder the sensor module 2001 and the semi-rigid coaxial cable 2015. Moreover, a problem arises in that there is a need to provide a process step for firmly fixing the sensor module 2001 to the multilayer circuit board 2002.